Carbon nanoparticle for highly sensitive and selective fluorescent detection of mercury(II) ion in aqueous solution

Recent Progress in Nanoparticles Based Sensors for the Detection of Mercury (II) Ions in Environmental and Biological Samples

To maintain a green and sustainable environment for human beings, rapid detection of potentially toxic heavy metals like mercury (Hg(II)) has attracted great attention. Recently, sensors have been designed which can selectively detect Hg(II) over other common available cations and give a naked eye or fluorometric response. In the last two decades, the trend is shifting from bulky organic chemosensors toward nanoparticles due to their rapid response, low cost, eco-friendly and easy synthesis. In this review, promising nanoparticles-based sensors for Hg(II) detection are discussed. The nano-sensors are functionalized with nucleotide or other suitable materials which coordinate with Hg(II) ions and give clear color or fluorescence change. The operational mechanisms are discussed focusing on its four basic types. The nanoparticles-based sensors are even able to detect Hg in three different oxidation states (Hg(II), Hg(I) and Hg(0)). Recently, the trend has been shifted from ordinary nanoparticles to magnetic nanoparticles to simultaneously detect and remove Hg(II) ions from environmental samples. Furthermore, the nano-sensors for Hg(II) are compared with each other and with the reported organic chemosensors.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

Non-aqueous onion like nano-carbons from waste diesel-soot used as FRET-based sensor for sensing of nitro-phenols

Herein, a simple-functionalization method is described to prepare the oleylamine functionalized non-aqueous version of onion-like nanocarbons (ONC-OA), where ONC was isolated from the waste pollutant soot exhausted from the diesel engine. The surface group analysis of ONC-OA has been investigated via Nuclear Magnetic Resonance and X-ray Photoelectron Spectroscopy. ONC-OA shows blue fluorescence with a quantum yield of ∼6% in tetrahydrofuran (THF). The fluorescence-based sensing applications of ONC-OA has been investigated for selective sensing of toxic aromatic nitro-phenols compounds (para-nitro, dinitro, and trinitro phenols) from the tested many nitro organic compounds. Based on the limit of detection values, ONC-OA shows much better results for tri-nitro phenol compared to di and mono nitrophenol. To understand the quenching mechanism, a time-resolved photoluminescence analysis of the sensor with and without the addition of quenchers is performed. The effective lowering in fluorescence lifetime of the sensor after the addition of quenchers concludes that the quenching observed is majorly due to the Förster Resonance Energy Transfer (FRET) mechanism. The real-life application of ONC-OA was analyzed by external spiking of N-PhOHs in soil samples.

Heavy Metal Ions Trigger a Fluorescent Quenching in DNA–Organic Semiconductor Hybrid Assemblies

The significance of DNA is no longer limited to its role as a biological information carrier; as a natural polymer, it also become in the field of materials. Single-stranded DNA (ssDNA) molecules with specific sequences can form a G-quadruplex or hairpin-shaped conformation with specific heavy metal ions through coordination bonds. In this study, ssDNA molecules of the four sequences were prepared into hybrid assemblies with one of the famous display materials, the tris-(8-hydroxyquinoline)aluminum (Alq₃) semiconductor. Based on these hybrid assemblies, heavy metal ions, namely Pb²⁺, Hg²⁺, Cd²⁺ and As³⁺, were detected individually at the ppb level. Apart from this, in practical application, many samples containing heavy metal ions are digested with acid. By introducing MES buffer solution, the influence of acidity on the fluorescent signal of Alq₃ was excluded. This strategy showed promising results in the practical application of detecting heavy metal ions in shrub branches and leaves.

Fluorescence sensing by carbon nanoparticles

Sensing is one of the most important fields in which chemists, engineers and other scientists are involved to realize sensoristic devices that can detect different analytes, both chemicals and biologicals. In this context, fluorescence sensing paves the way for the realization of smart sensoristic devices due to the possibility to detect the target analyte via a change in colour or emission. Recently (since 2006), carbon nanoparticles, which are a "new class" of nanostructures based on carbon atoms, have been widely used in sensing applications due to their intriguing optical properties. The scientific literature on this topic started from 2006 and a progressive increase in the corresponding number of publications has been observed. This review summarises the application of carbon nanoparticles in the sensing field, focusing on chemical and ion sensing.

A paper-based visualization chip based on nitrogen-doped carbon quantum dots nanoprobe for Hg(Ⅱ) detection

Hg(II) is one of the most toxic heavy metal ions. The bioconcentration and degradation-resistant of Hg(II) bring about serious harm to the ecosystem and humans. Therefore, the establishment of an accurate and effective method for detecting mercury ions is of great significance to environmental protection, food safety and human health. In this work, a new fluorescent nanoprobe was presented using nitrogen-doped carbon quantum dots (N-CQDs) for Hg(II) sensing with high stability and selectivity. On this basis, a paper-based chip was innovatively developed for visualization detection of Hg(II). The N-CQDs were prepared through a one-step hydrothermal reaction using catechol and ethylenediamine as carbon and nitrogen sources, respectively. As-prepared N-CQDs exhibit the strong green fluorescence at the excitation/emission wavelength of 370/511 nm. In aqueous solution, a rapid and highly sensitive detection method of Hg(II) was established by the joint of dynamic and static quenching effect of Hg(II) on N-CQDs fluorescence. Under the optimized conditions, there was a stable correlation between the fluorescence intensity change of N-CQDs and the concentrations of Hg(II) in the range of 15 ∼ 10⁴ nM, and the detection limit was down to 8 nM (S/N = 3). The recoveries of water, sorghum and rice were 91.60 to 102.46%, which was consistent with ICP-MS. More importantly, the N-CQDs nanoprobe was further integrated in nitrocellulose membrane to develop paper-based chip for Hg(II) visualization detection, and the detection performance was also excellent. This strategy had significant implications for achieving low-cost, on-site real-time monitoring of mercury (II) in the environment and food.

Catalytic oxidation of O-phenylenediamine by silver nanoparticles for resonance Rayleigh scattering detection of mercury (II) in water samples

In this study, a facile nanoparticle catalytic sensor for resonance Rayleigh scattering quantification of mercury (II) ion was developed. The developed approach is relied on the selective inhibition of the peroxidase-like activity of polyvinylpyrrolidone-stabilized silver nanoparticles (PVP-Ag-NPs) by mercury (II) ions. The synthesized PVP-Ag-NPs oxidize the aqueous solution of O-Phenylenediamine (colorless) to 2,3-phenazinediamine (bright yellow) and their resonance Rayleigh scattering (RRS) activity was completely suppressed. When mercury (II) was introduced, the RRS activity of PVP-Ag-NPs was turned on combined with a reduction of the intensity of the yellow color. The enhancement in the RRS intensity was related to the concentration of mercury (II) in the linear range of 10-2000 nM. The smaller size (4.5 nm), the large surface area and the uniform size (PDI = 0.379) of the synthesized PVP-Ag-NPs offered a higher chance for interaction between mercury (II) and PVP-Ag-NPs with the advantages of high sensitivity (LOD = 4 nM) and excellent selectivity for mercury (II) detection over several metals and anions.

Carbon dots for cancer nanomedicine: a bright future

Cancer remains one of the main causes of death in the world. Early diagnosis and effective cancer therapies are required to treat this pathology. Traditional therapeutic approaches are limited by lack of specificity and systemic toxicity. In this scenario, nanomaterials could overcome many limitations of conventional approaches by reducing side effects, increasing tumor accumulation and improving the efficacy of drugs. In the past few decades, carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and carbon dots) have attracted significant attention of researchers in various scientific fields including biomedicine due to their unique physical/chemical properties and biological compatibility and are among the most promising materials that have already changed and will keep changing human life. Recently, because of their functionalization and stability, carbon nanomaterials have been explored as a novel tool for the delivery of therapeutic cancer drugs. In this review, we present an overview of the development of carbon dot nanomaterials in the nanomedicine field by focusing on their synthesis, and structural and optical properties as well as their imaging, therapy and cargo delivery applications.

Highly Sensitive Detection for Mercury Ions Using Graphene Oxide (GO) Sensors

The mercury ion (Hg²⁺) is one of the heavy metal ions, and its presence in trace amounts can cause physiological damage to an organism. Traditional methods of Hg²⁺ detection have been useful but have also had numerous limitations and challenges, and as a result, it is important to design new and sophisticated methods that can aid in the detection of Hg²⁺. In this paper, two fluorescent dyes, carboxyfluorescein (FAM) and SYBR Green I, were used to label and intercalate DNA probes immobilized on the surface of graphene oxide (GO) for sensors to detect Hg²⁺. FAM and SYBR Green I dye share close excitation and emission wavelength spectra, which can promote and amplify the detection of signals, and also increase the limit of detection (LOD). The results showed that the limit of detection in this method was 0.53 nM. Moreover, when the sensors with double amino groups on the surface of GO were carried out to detect Hg²⁺, a limit of detection was improved to 0.43 nM. The sensors were then applied in the real sample. The results show that this method has a promising potential in Hg²⁺ detection.

A novel coumarin-based colorimetric and fluorescent probe for detecting increasing concentrations of Hg2+ in vitro and in vivo

Mercury has complex biological toxicity and can cause a variety of physiological diseases and even death, so it is of great importance to develop novel strategies for detecting trace mercury in environmental and biological samples. In this work, we designed a new coumarin-based colorimetric and fluorescent probe CNS, which could be obtained from inexpensive starting materials with high overall yield in three steps. Probe CNS could selectively respond to Hg²⁺ with obvious color and fluorescence changes, and the presence of other metal ions had no effect on the fluorescence changes. Probe CNS also exhibited high sensitivity against Hg²⁺, with a detection limit as low as 2.78 × 10^-8 M. More importantly, the behavioral tracks of zebrafish had no obvious changes upon treatment with 10 μM probe CNS, thus indicating its low toxicity. The probe showed potential application value and was successfully used for detecting Hg²⁺ in a test strip, HeLa cells and living zebrafish larvae.

Acid Oxidation of Muskmelon Fruit for the Fabrication of Carbon Dots with Specific Emission Colors for Recognition of Hg2+ Ions and Cell Imaging

In this study, water-soluble emissive carbon dots (CDs) are effectively fabricated with specific optical properties and colors by acid oxidation of muskmelon (Cucumis melo) fruit, which are termed as C. melo CDs (CMCDs). The fluorescence properties of CMCDs were tuned by controlling the experimental conditions that allow them to emit different colors, that is, blue (B-), green (G-), and yellow (Y-) CMCDs, with different emission wavelengths at 432, 515, and 554 nm when excited at 342, 415, and 425 nm, respectively. The fabricated multicolor-emissive CDs were confirmed by various analytical techniques. The sizes of B-, G-, and Y-CMCDs were found to be ∼3.5, ∼4.3, and ∼5.8 nm, respectively. The as-prepared CMCDs display stable emissions with quantum yields of 7.07, 26.9, and 14.3% for the three CMCDs, which could act as a promising probe for the selective detection of Hg²⁺ ions. Upon the addition of Hg²⁺ ions, the fluorescence intensity of G-CMCDs at 515 nm was quenched largely than that of B- and Y-CMCDs. The spectroscopic results display that the G-CMCDs acted as a sensor for the detection of Hg²⁺ ions with a wide linear range from 1.0 to 25 μM (R ² = 0.9855) with a detection limit of 0.33 μM. This method was successfully applied to detect Hg²⁺ ions in biological and water samples. The fabricated multicolor-emissive CMCDs possess the cell (Cunninghamella elegans, Aspergillus flavus, and Rhizoctonia solani) imaging property, suggesting the biocompatible nature for multicolor imaging of various cells.

Band gap tuning and surface modification of carbon dots for sustainable environmental remediation and photocatalytic hydrogen production - A review

Energy and water are the two major issues facing the modern mankind. Providing freshwater requires energy and producing energy uses water. In the present-day scenario, both these routes face growing problems and limitations. Energy crisis has risen due to the depletion of fossil fuels that cause pollution to water bodies making the water unusable for human consumption. In this regard, semiconductor nanocrystals with luminescent properties or carbon quantum dots (CQDs) are the newly developed nanomaterials whose distinctive photo-physical characteristics are focusing to a new generation of robust materials and sensors for sustainable development. In this review, advances in surface and band gap modification of CQDs to improve the activity of nanomaterials will be discussed with special reference to some specific CQDs exhibiting special optical properties for water treatment/splitting applications. Recent advances on CQDs nanocomposites including their applications in photodegradation of organic pollutants, sensing of heavy metal ions in water and water splitting are discussed critically to narrate the future prospects in this field. Challenges and limitations for further improvement are covered to provide smart choices for creating sustainability of benign environment and economic benefits.

A carbon dot-based fluorescent nanoprobe for the associated detection of iron ions and the determination of the fluctuation of ascorbic acid induced by hypoxia in cells and in vivo

Maintaining the redox balance of biological systems is a key point to maintain a healthy physiological environment. Excessive iron ions (Fe³⁺) can cause apoptosis, tissue damage and death. Fortunately, ascorbic acid (AA) as a reducing agent has been evaluated for the reduction of Fe³⁺. Moreover, AA plays an important role in relieving hypoxia-induced oxidative stress. Therefore, the real-time imaging of the Fe³⁺ and AA fluctuations is important for understanding their biofunctions in cells and in vivo. In this work, we developed a fluorescent nanoprobe carbon dot-desferrioxamine B (CD-DB) by the conjugate connection of CDs and desferrioxamine B (a complexing agent for Fe³⁺) for the associated detection of Fe³⁺ and AA. CD-DB exhibited excellent sensitivity and selectivity for the detection of Fe³⁺ and AA. The nanoprobe CDs-DB@Fe obtained by the reaction of CD-DB and Fe³⁺ was suitable for tracing the dynamic changes of AA in cells and in vivo. Therefore, CDs-DB@Fe was used for monitoring the fluctuation of AA in hypoxic cell models, hypoxic zebrafish models and liver ischemia mice models. These results exhibited the decrease in AA under hypoxic conditions because AA was consumed to neutralize free radicals and relieve hypoxia-induced oxidative stress damage. The ideal biocompatibility and low toxicity make our nanoprobe a potential candidate for the research of the physiological effects of AA in vivo.

Green Hydrothermal Synthesis of N-doped Carbon Dots from Biomass Highland Barley for the Detection of Hg2

Totally water-soluble N-doped Carbon dots (N-CDs) were synthesized by a green hydrothermal method from biomass using Highland barley as a carbon source and ethanediamine as nitrogen source. TEM and XRD showed the graphitic amorphous structure and narrow diameter distribution of these N-CDs. N-doping to the crystal lattice and carrying many hydrophilic groups on the surface of N-CDs were verified by XPS and FT-IR. The as-synthesized N-CDs emitted strong blue fluorescence at 480 nm and owned a relatively high quantum yield of 14.4%. The product also could sensitively and selectively detect Hg2+ ions in the range of 10-160 μM and the limit of detection was equal to 0.48 μM.

A specific electrochemiluminescence sensor for selective and ultra-sensitive mercury(ii) detection based on dithiothreitol functionalized copper nanocluster/carbon nitride nanocomposites

A novel electrochemiluminescence sensor based on the combination of copper nanoclusters and carbon nitride nanosheets was fabricated for detecting Hg²⁺.

A reliable amplified fluorescence-enhanced chemosensor (Eu-MIL-61) for the directional detection of Ag+ in an aqueous solution

A robust gallium carboxylate Ga(OH)(btec)·0.5H₂O (MIL-61) was synthesized under mild hydrothermal conditions and selected as the parent MOF to prepare Eu-MIL-61 by post-synthetic modification due to the uncoordinated carbonyl group of the ligand (pyromellitic acid (H4btec)). The firm framework, permanent porosity, and non-coordinated sites make MIL-61 a good scaffold for immobilizing and sensitizing Eu³⁺. The products showed excellent luminescence and, more significantly, Eu-MIL-61 showed excellent selectivity with photoluminescence enhancement, fast response time, and low detection limit for Ag⁺ ions in the aqueous solutions. In addition, the frameworks were not susceptible to the acid-base property of solutions, which can be further applied to monitor the concentration of Ag⁺ in several daily water samples.

Using silicon-coated gold nanoparticles to enhance the fluorescence of CdTe quantum dot and improve the sensing ability of mercury (II)

The effect of silicon-coated gold nanoparticles with different gold core diameter and silica shell thickness on the fluorescence emission of CdTe quantum dots (QDs) was investigated. For gold nanoparticles with a diameter of 15nm, silica coating can only results in fluorescence recover of the bare gold nanoparticle-induced quenching of QDs. However, when the size of gold nanoparticle is increased to 60nm, fluorescence enhancement of the QDs could be obtained by silica coating. Because of the isolation of the silica shell-reduced quenching effect and local electric field effect, the fluorescence of QDs gets intense firstly and then decreases. The maximum fluorescence enhancement takes place as the silica shell has a thickness of 30nm. This enhanced fluorescence from silicon-coated gold nanoparticles is demonstrated for sensing of Hg²⁺. Under optimal conditions, the enhanced fluorescence intensity decreases linearly with the concentration of Hg²⁺ ranging from 0 to 200ng/mL. The limit of detection for Hg²⁺ is 1.25ng/mL. Interference test and real samples detection indicate that the influence from other metal ions could be neglected, and the Hg²⁺ could be specifically detected.

A novel fluorescent aptasensor for ultrasensitive and selective detection of acetamiprid pesticide based on the inner filter effect between gold nanoparticles and carbon dots

A novel fluorescent aptasensor based on the inner filter effect of carbon dots has been proposed for the ultrasensitive and selective detection of acetamiprid pesticide in vegetable samples.

Carbon dots as absorbance promoter probes for detection of Cu(ii) ions in aqueous solution: central composite design approach

In this work, the use of carbon dots (CDs) as a complexing agent and sensitizer in a polymeric matrix for determination of copper(ii) by UV-vis spectroscopy is reported for the first time.

Design of novel and modified dual optode membrane based on carbon dots for both ultratrace copper(ii) and cobalt(ii): derivative spectrophotometric and central composite design study

A selective, accurate and highly sensitive optical chemical sensor (optode) for the simultaneous determination of copper(ii) and cobalt(ii) without any prior separation or purification ion sensing was developed.

A turn-on fluorescent sensor for highly sensitive mercury(ii) detection based on a carbon dot-labeled oligodeoxyribonucleotide and MnO2 nanosheets

ssDNA–QDs can bind to MnO₂ nanosheets with a higher appetency than dsDNA–QDs.

Gas assisted method synthesis nitrogen-doped carbon quantum dots and Hg (II) sensing

Nitrogen-doped fluorescent carbon quantum dots (CQDs) was prepared by gas-assisted method using cellulose as precursors under ammonia atmosphere, which not only exhibited excellent photoluminescent properties, but also showed highly selective and sensitive detection of mercury ion. The nitrogen-doped CQDs displayed excitation wavelength dependent fluorescent behavior with outstanding dispersibility. Moreover, they exhibited high tolerance to various external conditions, such as storage time, pH value, and ionic strength. The rapid detection of Hg (II) by one-step operation within 1 min and the good linear correlation between I₀/I and Hg (II) concentration in the range of 10-100 nM made the nitrogen-doped CQDs a promising nanoprobe for Hg (II) detection. The detection limit of the nitrogen-doped CQDs is about 7.7 nM. Such a nanoprobe has been successfully applied for the analysis of Hg (II) in natural water samples, demonstrating excellent practical feasibility.

Carbon dots for fluorescent detection of α-glucosidase activity using enzyme activated inner filter effect and its application to anti-diabetic drug discovery

Recently, α-glucosidase inhibitor has been widely used in clinic for diabetic therapy. In the present study, a facile and sensitive fluorescent assay based on enzyme activated inner filter effect (IFE) on nitrogen-doped carbon dots (CDs) was first developed for the detection of α-glucosidase. The N-doped CDs with green emission were prepared by a one-step hydrothermal synthesis and gave the fluorescence quantum yield of 30%, which were used as the signal output. Through α-glucosidase catalysis, 4-nitrophenol was released from 4-nitrophenyl-α-d-glucopyranoside (NGP). Interestingly, the absorption of 4-nitrophenol and the excitation of CDs were completely overlapping. Due to its great molar absorptivity, 4-nitrophenol was capable of acting as a powerful absorber to affect the fluorescent signal of CDs (i.e. IFE). By converting the absorption signals into fluorescence signals, the facile fluorescence assay strategy could be realized for α-glucosidase activity sensing, which effectively avoided the complex modification of the surface of CDs or construction of the nanoprobes. The established IFE-based sensing platform offered a low detection limit of 0.01 U/mL (S/N = 3). This proposed sensing approach has also been expanded to the inhibitor screening and showed excellent applicability. As a typical α-glucosidase inhibitor, acarbose was investigated with a low detection limit of 10^-8 M. This developed method enjoyed many merits including simplicity, lost cost, high sensitivity, good reproducibility and excellent selectivity, which also provided a new insight on the application of CDs to develop the facile and sensitive biosensor.

Fe-nitrilotriacetic acid coordination polymer nanowires: an effective sensing platform for fluorescence-enhanced nucleic acid detection

The determination of specific nucleic acid sequences is key in identifying disease-causing pathogens and genetic diseases. In this paper we report the utilization of Fe-nitrilotriacetic acid coordination polymer nanowires as an effective nanoquencher for fluorescence-enhanced nucleic acid detection. The detection is fast and the whole process can be completed within 15 min. This nanosensor shows a low detection limit of 0.2 nM with selectivity down to single-base mismatch. This work provides us with an attractive sensing platform for applications.

Fluorescent nitrogen and sulfur co-doped carbon dots from casein and their applications for sensitive detection of Hg2+ and biothiols and cellular imaging

Fluorescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized by a one-step pyrolysis strategy using casein as carbon, nitrogen and sulfur sources, and characterized by UV-vis spectrum, fluorescent spectrum, X-ray photoelectron spectroscopy (XPS) and FT-IR, etc. The synthesized NSCDs displayed a blue emission under ultraviolet illumination with a quantum yield of 31.8%, and a good aqueous solubility, photostability and biocompatibility. It was found that the fluorescence intensity of NSCDs could be selectively quenched by Hg²⁺, so NSCDs was used as an effective probe for the detection of Hg²⁺. The linear range and the limit of detection (LOD) of the fluorescent sensor based on NSCDs for the detection of Hg²⁺ were 0.01-0.25 μM and 6.5 nM, respectively. Spiked water samples were detected by the sensor with the recovery of 95.4-106.3% and relative standard deviation (RSD) of 3.6-8.6%. It was also observed that the quenched NSCDs-Hg²⁺ system could be restored by the addition of biothiols such as l-cysteine (Lcy), homocysteine (Hcy) and glutathione (GSH), thus NSCDs-Hg²⁺ system was employed as a fluorescent sensor for the detection of biothiols. The linear range and LOD of the NSCDs-Hg²⁺ system were 1-10 μM and 23.6 nM for Lcy, 0.2-2.5 μM and 12.3 nM for Hcy, and 0.1-2.0 μM and 16.8 nM for GSH, respectively. The NSCDs-Hg²⁺ system was applied for the detection of biothiols in serum samples with satisfied results. In addition, the study in vitro imaging HeLa cells revealed that the synthesized NSCDs could be used as effective fluorescent probes in cellular imaging without noticeable cytotoxicity.

Design and construction of a new optical solid-state mercury(ii) sensor based on PVC membrane sensitized with colloidal carbon dots

A new Hg²⁺ ion solid-state double layer sensor impregnated with colloidal carbon dots and N′-(3-(4-(dimethylamino)phenyl)allylidene)isonicotinohydrazide (NDPAI, as a second layer) was inserted in plasticized polyvinyl chloride (PVC) as the first layer.

Recent advances in nanomaterials for water protection and monitoring

Nanomaterials (NMs) for adsorption, catalysis, separation, and disinfection are scrutinized. NMs-based sensor technologies and environmental transformations of NMs are highlighted.

Aconitic acid derived carbon dots as recyclable “on–off–on” fluorescent nanoprobes for sensitive detection of mercury(ii) ions, cysteine and cellular imaging

Aconitic acid is used as a new precursor for fabricating CDs and developing a sensitive “on–off–on” sensor for Hg²⁺, Cys and cellular imaging.

Rapid detection of mercury contamination in water by surface enhanced Raman spectroscopy

Mercury (Hg) is a potent neurotoxin in fish, wildlife, and humans.

DNA-stabilized silver nanoclusters and carbon nanoparticles oxide: A sensitive platform for label-free fluorescence turn-on detection of HIV-DNA sequences

Based on the remarkable difference between the interactions of carbon nanoparticles (CNPs) oxide with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), and the fact that fluorescence of DNA-stabilized silver nanoclusters (AgNCs) can be quenched by CNPs oxide, DNA-functionalized AgNCs were applied as label-free fluorescence probes and a novel fluorescence resonance energy transfer (FRET) sensor was successfully constructed for the detection of human immunodeficiency virus (HIV) DNA sequences. CNPs oxide were prepared with the oxidation of candle soot, hence it is simple, time-saving and low-cost. The strategy of dual AgNCs probes was applied to improve the detection sensitivity by using dual- probe capturing the same target DNA in a sandwich mode and as the fluorescence donor, and using CNPs oxide as the acceptor. In the presence of target DNA, a dsDNA hybrid forms, leading to the desorption of the ssDNA-AgNCs probes from CNPs oxide, and the recovering of fluorescence of the AgNCs in a HIV-DNA concentration-dependent manner. The results show that HIV-DNA can be detected in the range of 1-50nM with a detection limit of 0.40nM in aqueous buffer. The method is simple, rapid and sensitive with no need of labeled fluorescent probes, and moreover, the design of fluorescent dual-probe makes full use of the excellent fluorescence property of AgNCs and further improves the detection sensitivity.

An ideal detector composed of a 3D Gd-based coordination polymer for DNA and Hg2+ ion

A 3D Gd-based CP was employed as an effective fluorescent sensing platform for DNA and Hg²⁺ ion detection with sensitivity and selectivity, due to its ability to highly quench fluorescence and its different affinities toward ssDNA and dsDNA.